Microscope objectives in which lens groups can be moved along the optical axis are known per se. Moving serves, e.g., to adapt the objective to different cover slip thicknesses, different immersion liquids or different operating temperatures, or it is generally intended for the correction of imaging quality.
An example known in prior art is shown in FIGS. 1.1 through 1.5 (accordingly marked as “PRIOR ART” therein). By means of a cam 1 machined on a driving ring 6 that can be rotated about the optical axis of a lens group 3, a pin 4 is moved in axial direction. The pin 4 is mechanically firmly connected with the lens group 3. A slotted hole 2, machined into a fixed sleeve 5 that concentrically encloses the lens group, prevents the pin 4 from rotation about the optical axis while it is moved. This also secures the lens group 3 against rotation.
A lens group 3 in the sense of the invention described below is understood to be a self-contained assembly consisting of one or several optical lenses enclosed by a lens mount. For the sake of clarity, the lens mount is not shown here.
To eliminate the axial slackness between pin 4 and cam 1 shown in FIG. 1.4, frequently a spring element (not shown on the drawing) is provided within the sleeve 5. The disadvantage of this is the possible soiling of the optical system by abrasion at the contact surfaces of the spring element. Eliminating the axial slackness is important especially if, within the objective, several lens groups 3 are provided in axial succession, the distances between them are to be varied according to the principle described above. If the amounts of slackness between the pins 4 and the cams 1 differ from each other, the lens groups 3 will not start to move simultaneously when the direction of movement is reversed, which results in undesirable optical aberrations. Analogously this also applies to a rotation of the pins 4 and, thus, of the lens groups 3 relative to each other, which results in undesirable optical aberrations such as astigmatism or coma.
Another known possibility to move the lens group 3 is shown in FIGS. 2.1 through 2.5 (accordingly also marked as “PRIOR ART” therein). Here, instead of the driving ring 6 shown in FIG. FIG. 1.2, two mutually engaged threaded rings 7 and 8 are provided. The pin 4 is held in the inner threaded ring 7 in a drilled hole 9 rather than in a slotted hole. The axial moving of the lens group 3 is controlled by means of rotation of the outer threaded ring 8 and the thread lead. A spring element (not shown) can be attached outside the sleeve 5 to avoid soiling within the optical system due to abrasion. For the reasons already described above, here, too, the slackness between pin 4 and sleeve 5 must be very small. For the sake of clarity, the lens mount is not shown in FIGS. 2.1 through 2.5 either.
In both versions, the moving of the lens group 3 is intended to be manual. Especially in microscopes of inverted design, this is a disadvantage, because the objectives are arranged below the table, so that their accessibility is restricted. Settings necessary to the objective can be done only awkwardly, if at all.
To remedy this problem, a control device for control elements in microscope objectives, described in DE 10 2008 026 774 A1, is provided with motor drives. At least two lens groups can be moved along the optical axis of the microscope objective by means of allocated adjusting collars, each of which can be motor-driven. Transmitting the rotary movement of the motors to the adjusting collars is effected via gears; a control unit is provided in which characteristic curves for different amounts of travel of the control elements are stored and can be activated.
WO 08/100695 A2 describes the motor drive of the correction mechanism for objectives by means of motors provided on the revolving nosepiece and connected to the objectives via a tape. This solution is complex and requires a lot of space.
In a scanning microscope according to EP 1 319 968 B1, all lenses of the objective are enclosed by a common mount; they are adjusted along the optical axis in common, by means of an electromagnetic moving coil. Adjustment of individual lenses is not possible here.
As a disadvantage, the coupling of motor drives to a guideway for the lens groups, a feature already provided in high-grade microscope objectives, cannot be achieved with the technical solutions known in prior art.
The invention described below is based on the problem of eliminating the disadvantages found in prior art.
According to the invention, this problem is solved by the features specified in independent claims 1, 12, and 19. Advantageous embodiments are stated in the dependent claims 2 through 11, 13-18, and 20.
According to the invention, a microscope objective of the kind addressed hereby and described, depicted, and claimed herein includes: a motor producing a rotational drive movement, and transmission elements designed to convert the rotational movement into a translational movement, to transmit the translational movement to the lens group, and simultaneously to prevent any rotation of the lens group about the optical axis.
In a first embodiment, the rotating output shaft of the motor is joined to a screw spindle that engages with a translationally (or linearly) movable nut, with coupling elements being provided for transmitting the translational movement of the nut to the lens group. The coupling elements are guided along the optical axis in a constrained manner, so as to prevent their rotation and, thus, the rotation of the lens group, about the optical axis.
In a second embodiment, the rotating output shaft of the motor is also joined to a screw spindle, which in this case, however, is engaged with a threaded hole provided in the lens mount, so that—without any interposed coupling elements—the lens group is translationally moved in a direct manner. Because of the direct engagement of the screw spindle with the lens mount, both the translational movement of the lens group and the latter's securing against rotation about the optical axis are achieved.
In connection with the second embodiment, the lens group may be provided with supplementary elements for its constrained guidance along the optical axis, so that it is specially secured against rotation about the optical axis.
In both embodiments, the axis of rotation of the drive motion is preferably aligned parallel to the optical axis.
In further embodiments, the motor, the transmission elements and the coupling elements (the latter at least in part) may be accommodated either in the space between the lens mount and a sleeve enclosing the lens mounts or outside this sleeve.
Further, it is of advantage if the movable lens group is assigned a measuring device that delivers a measured value serving as a reference for the amount of travel and thus provides the basis for a higher positioning accuracy in the moving of the lens group. For this purpose, the motor may be provided with an encoder (e.g., a rotary encoder of either the optical or mechanical variety, or the like). To avoid hysteresis, a spring element may be provided between the motor output and the nut, which eliminates the slackness between the screw spindle and the nut.
With reference to the prior art cited hereinabove, the premise of this disclosure includes, among other things, the replacement of the manually operated driving rings or ring nuts by an electromechanical drive motor that generates a rotational drive movement. The axis of rotation should be aligned parallel to the optical axis of the microscope objective. The transmitting mechanism, or components of a transmission, can include a spindle connected to the output shaft of the motor, which effects the precise linear motion in axial direction along the optical axis of the objective and, thus, simultaneously the securing of the lens group against rotation about the optical axis. Thus, the linear motion of the lens group along the optical axis of the microscope is promoted while the rotary motion of the lens group is resisted. The motor and such components of the height adjustment, height selection, or height-setting, mechanism as are essential for its function may, depending on the embodiment hereof utilized, be located either in the space between the lens mount and a sleeve enclosing the lens mount, or outside this sleeve, or in an embodiment having more than one motor coupled to a discrete lens group a combination of both, for example.
In another embodiment, the measuring device is arranged at the sleeve of the microscope objective. The movable part of the measuring device may be linked to a driver so as to permit a compact design of the motorized microscope objective.
In a further embodiment a microscope objective is provided that includes: at least one lens group movable along an optical axis of a microscope objective, wherein said at least one lens group includes at least one optical lens coupled to a lens mount; an electromechanical rotary motor having a driven end portion; a plurality of transmission elements coupled at a proximal end to the driven end portion and configured to provide linear motion to a distal end portion of the elements, wherein the distal end portion mechanically couples to the at least one lens group; and structure coupled to the at least one lens group and configured to allow linear motion of the at least one lens group along the optical axis and to resist rotational motion of the at least one lens group relative to the optical axis. In yet a further embodiment, a microscope objective according to the foregoing further includes means for sensing an elevation of the at least one lens group relative to a reference elevation and providing an output signal related to the elevation relative to the reference elevation.
If more than one lens group are to be moved, a number of motors corresponding to the number of the lens groups, with associated setting mechanisms, e.g., in the form of the screw spindle and additional transmission elements, may be provided.